JP5213119B2 - Method for removing lead from cement firing furnace - Google Patents

Description

  The present invention relates to a method for removing lead from a cement firing furnace, and in particular, lead from dust contained in a gas extracted from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. It is related with the method of removing lead from a cement baking furnace by collect | recovering.

  Conventionally, since lead (Pb) in cement is immobilized, it has been considered that there is no elution into soil. However, as the amount of recycled resources used in cement production equipment has increased in recent years, the amount of lead in cement has also increased, and the content has been greatly exceeded. Since there is a possibility of elution into the soil as the concentration increases, it is necessary to reduce the lead concentration in the cement to the level of the conventional content.

  Therefore, as a technique for reducing the lead concentration in cement, for example, Patent Document 1 discloses that waste water is washed in order to effectively separate and remove chlorine and lead in waste supplied to the cement manufacturing process. A step of alkali elution of the filtered solid content, a deleading step of precipitating and separating lead from the filtrate, a decalcifying step of precipitating and separating calcium from the deleaded filtrate, and heating the filtrate Thus, a waste processing method including a salt recovery step of separating and recovering chloride by precipitation is disclosed.

  Further, in Patent Document 2, in separating and removing lead and the like from waste such as fly ash, a solution containing calcium ions is mixed to obtain a slurry, followed by solid-liquid separation and solid content containing zinc. And a process for obtaining an aqueous solution containing lead, and a process for adding a sulfurizing agent to the aqueous solution containing lead, followed by solid-liquid separation to obtain a solution containing lead sulfide and calcium ions, etc. A method is described.

Japanese Unexamined Patent Publication No. 2003-1218 Japanese Unexamined Patent Publication No. 2003-201524

  However, in the prior art described in the above patent document, when reducing the amount of lead in the cement, a part of the combustion gas is extracted from the kiln exhaust gas passage from the kiln bottom of the cement kiln to the lowermost cyclone. Although the lead content in the chlorine bypass dust recovered from the generated gas is removed, the proportion of lead removed from the chlorine bypass dust to the outside of the system is only about 30%, even in the chlorine bypass dust. Even if 100% of the lead is removed, the remaining 70% is still taken into the clinker discharged from the cement kiln, so it is not easy to reduce the lead content of the cement. Therefore, it is important to promote the volatilization of lead in the cement kiln and increase the concentration ratio of lead into chlorine bypass dust.

  As the lead volatilization technique, a chloride volatilization method and a reduction volatilization method are known. However, if the chlorination volatilization method that is generally performed is applied to the cement firing step, it is necessary to input a much larger amount of chlorine than a common amount in cement production. On the other hand, the application of the reduction volatilization method is problematic in terms of cement quality because the color of the cement is yellow.

  Therefore, the present invention has been made in view of the above problems in the prior art, and promotes the volatilization of lead in the cement kiln without affecting the quality of the cement. An object of the present invention is to provide a method for efficiently reducing the lead content of cement by increasing the concentration ratio of lead into the cement.

To achieve the above object, the present invention provides a lead removal process from cement kilns, the O ₂ concentration of combustion gas in the kiln of the cement kiln 5% or less and / or a CO concentration on 1000ppm than And control, a region of the kiln kiln near the bottom of the cement kiln where the temperature of the raw material in the cement kiln is 800 to 1100 ° C. is made a reducing atmosphere, a part of the combustion gas of the cement kiln is extracted, and the dust contained in the combustion gas And collecting lead from the collected dust.

  And according to this invention, since the raw material temperature in a cement kiln near the kiln bottom of a cement kiln is made into the reducing atmosphere, the volatility of lead can be raised significantly. By extracting a part of the cement kiln combustion gas, collecting dust contained in the combustion gas, and collecting lead from the collected dust, the lead content of the cement can be efficiently reduced. Further, according to this method, the cement quality is not affected.

In the method for removing lead from the cement firing furnace, the O ₂ concentration of the combustion gas at the kiln bottom of the cement kiln is controlled to 5% or less and / or the CO concentration to 1000 ppm or more, and the inner diameter of the cement kiln is D, When the distance from the bottom of the cement kiln toward the inside of the kiln in the longitudinal direction is L, a raw material containing fuel and / or combustible material is introduced into a region where the L / D of the cement kiln is 0 or more and 12 or less. be able to. Thereby, the reducing atmosphere of the area | region whose raw material temperature in the said cement kiln is 800-1100 degreeC can be maintained reliably, and the lead content rate of cement can be reduced further efficiently.

  In the method for removing lead from the cement firing furnace, a raw material containing powdered and / or slurry fuel and / or combustible material is injected into a region where the L / D of the cement kiln is 0 or more and 12 or less using a nozzle. can do.

  Moreover, the raw material containing a block-shaped fuel and / or a combustible substance can be thrown into the area | region where L / D of the said cement kiln is 0-12.

  Further, a raw material containing a cylindrical or spherical fuel and / or a combustible material is introduced into an area where the L / D of the cement kiln is 0 or more and 12 or less using the inclined surface of the kiln bottom of the cement kiln. The raw material containing the cylindrical or spherical fuel and / or combustible material may be formed by molding a raw material containing a small piece of fuel and / or combustible material.

  Moreover, the raw material containing the said fuel and / or a combustible substance can be supplied from the inlet provided in the area | region where L / D of the said cement kiln is 0-12.

  As described above, according to the method for removing lead from a cement firing furnace according to the present invention, the lead content of cement can be efficiently reduced without affecting the quality of cement.

Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1A shows an example of an apparatus for carrying out a first embodiment of a method for removing lead from a cement firing furnace according to the present invention. This apparatus is a kiln bottom 10a side of a cement kiln 10 ( The raw material containing powdery and / or slurry fuel and / or combustible material (hereinafter referred to as “fuel etc.” as appropriate) is cement kiln on the end side where the calciner 11 and the lowermost cyclone 12 are provided) The nozzle 1 for injecting in 10 is provided.

  The nozzle 1 is provided with a fuel supply unit F (not shown) and an injection unit for injecting the fuel unit F supplied to the nozzle 1 into the cement kiln 10. The fuel unit F supplied to the nozzle 1 is supplied to the nozzle 1. It can be supplied to the back of the cement kiln 10.

  On the other hand, as shown in FIG. 2, the cement kiln 10 is provided with a chlorine bypass facility, and the extracted gas from the kiln exhaust gas passage from the bottom of the kiln 10 to the lowermost cyclone is cooled by the probe 21. After being cooled by the cold air from the fan 22, it is introduced into the classifier 23 and separated into coarse powder dust, fine powder and gas. The coarse powder dust is returned to the cement kiln system, and fine powder (chlorine bypass dust) containing potassium chloride (KCl) and the like is collected by the dust collector 24. The exhaust gas discharged from the dust collector 24 is released to the atmosphere through the exhaust fan 25.

  Next, a method for removing lead from a cement firing furnace according to the present invention using the above system will be described.

  In FIG. 1 (a), a raw material containing fuel or combustible material in powder or slurry form is injected into a cement kiln 10 using a nozzle 1. Here, various fuels such as pulverized coal, heavy oil and the like, which are generally used as the main fuel of the cement kiln 10, as well as waste fuel can be used as the fuel. Moreover, the kind of the raw material containing the combustible material is not limited, and the waste material may be reused. However, in the case of fuel with a high volatile content, even if a highly reducing gas is generated, it immediately flows downstream and is replaced with a highly oxidizing gas. Is preferred.

Using the nozzle 1, the fuel etc. F, the inside diameter of the cement kiln 10 (distance between opposing refractory surfaces) is D, and the distance from the kiln bottom 10 a side of the cement kiln 10 toward the inside of the kiln in the longitudinal direction is L In this case, L / D is injected into the region of 0 or more and 12 or less.

  3A to 3E show the relationship between the gas temperature and the volatilization rate of lead by chemical equilibrium simulation, the horizontal axis indicates the gas temperature, and the vertical axis indicates the volatilization rate of lead. 3A to 3E, (a) is a humid air atmosphere, (b) is a standard combustion gas atmosphere, (c) is an oxygen-free atmosphere, (d) is a low concentration CO atmosphere, (e ) Shows a high-concentration CO atmosphere, and as it goes from (a) to (e), it shifts from an oxidizing atmosphere to a reducing atmosphere, and (e) shows the strongest reducing atmosphere.

  As is clear from FIG. 3, the volatilization rate of lead is significantly increased in the region where the gas temperature is 700 to 1200 ° C. in the atmosphere of (e) having a strong reducing property, as compared with other cases. . This temperature range corresponds to a region near the kiln bottom 10a of the cement kiln 10. Therefore, by injecting powdered or slurry fuel or the like F into the region where the L / D of the cement kiln 10 is 0 or more and 12 or less, that is, the region where the raw material temperature in the cement kiln 10 is 800 to 1100 ° C. This region can be made a reducing atmosphere, and the volatilization rate of lead can be significantly increased.

  FIG. 4 is test data showing the relationship between the CO concentration of the combustion gas in the kiln bottom 10a of the cement kiln 10 (hereinafter referred to as “kiln bottom CO concentration”) and the lead volatilization rate. When the lead volatilization rate is 0.1% (1000 ppm) or more, the lead volatilization rate is about 90% or more, and when the kiln bottom CO concentration is 0.3% (3000 ppm) or more, the lead volatilization rate is about 95% or more. Thereby, it was demonstrated that the volatilization rate of lead significantly increases in the vicinity of the kiln bottom 10a of the cement kiln 10 shown in FIG. 1 under a highly reducing atmosphere.

FIG. 5 is test data showing the relationship between the O ₂ concentration of the combustion gas in the kiln bottom 10a of the cement kiln 10 (hereinafter referred to as “kiln bottom O ₂ concentration”) and the lead volatilization rate. When the O ₂ concentration is 5% or less, the lead volatilization rate is about 90% or more, and when the kiln bottom O ₂ concentration is 3% or less, the lead volatilization rate is about 95% or more. From now on, it was demonstrated that the volatilization rate of lead greatly increases in the region near the kiln bottom 10a of the cement kiln 10 shown in FIG.

  The lead volatilized in the cement kiln 10 is included in the gas extracted by the probe 21 in FIG. 2, and the extracted gas is cooled in the probe 21 and then introduced into the classifier 23, and the coarse dust, fine powder and It is separated into gas and fine powder is collected by the dust collector 24. This fine powder has a higher concentration of lead than in the past due to more volatilization of lead in the cement kiln 10, so the lead content of the cement produced in the cement kiln 10 can be reduced by collecting this lead. Can be reduced.

  FIG. 1B shows an example of an apparatus for carrying out the second embodiment of the method for removing lead from a cement firing furnace according to the present invention, and this apparatus is disposed on the kiln bottom 10 a side of the cement kiln 10. The long throwing device 2 for feeding the bulk fuel or the like F into the cement kiln 10 is provided. The long throwing device 2 is powered by an elastic body, air pressure, hydraulic pressure or the like, and is configured so that the fuel F or the like supplied to the nozzle 1 can be supplied to the back of the cement kiln 10.

  Using such a long caster 2, the fuel etc. F is injected into the region where the L / D of the cement kiln 10 is 0 or more and 12 or less, and the cement kiln 10 is the same as in the first embodiment. The raw material temperature in the region of 800 to 1100 ° C. can be reduced and the volatilization rate of lead can be significantly increased. As described above, lead is extracted from chlorine bypass dust in which lead is concentrated more than before. By collecting, the lead content of the cement manufactured by the cement kiln 10 can be reduced.

In the present embodiment, and the size of the fuel such as F, poured conditions such as initial velocity, fluid resistance R = C · A · ρ · u 2/2, (C: resistance coefficient, A: projected area, [rho : Density, u: relative speed) and the like can be calculated and determined from a fluid simulation or the like. As a result, the fuel etc. F is prevented from returning to the kiln bottom 10a side by the exhaust gas of the cement kiln 10, and the L / D of the cement kiln 10 is reliably 0 or more and 12 or less using the long throw device 2. The fuel F or the like can be introduced into the region.

  Further, the installation position of the long caster 2 is also preferably installed on the raw material side on the back of the cement kiln in order to prevent the fuel etc. F from returning. The exhaust gas of the cement kiln does not flow uniformly in the kiln, but preferentially flows on the anti-raw material side with less resistance. For this reason, when the fuel etc. F is thrown in, it is possible to prevent the fuel etc. F from returning by installing the long throwing device 2 on the raw material side with less ventilation resistance.

  FIG. 1 (c) is for explaining a third embodiment of the method for removing lead from a cement firing furnace according to the present invention. In this embodiment, the kiln bottom 10 a of the cement kiln 10 is shown. A cylindrical or spherical fuel F or the like is introduced using the inclined surface 3. The fuel or the like F is supplied to the back of the cement kiln 10 using the inertia of the cylindrical or spherical fuel or the like F that rolls on the inclined surface 3.

  Even in this case, the fuel or the like F is charged into the region where the L / D of the cement kiln 10 is 0 or more and 12 or less, and the raw material temperature in the cement kiln 10 is 800 to 1100 ° C. as in the above embodiment. The region can be reduced, the volatilization rate of lead can be increased, lead can be recovered from chlorine bypass dust enriched with more lead, and the lead content of the cement produced by the cement kiln 10 can be reduced.

  For the above-mentioned cylindrical or spherical fuel F or the like, the cementing kiln is more accurately estimated by predicting the arrival position from the charging height position and the burn-out time measured in advance with an electric furnace or the like. The fuel F or the like can be put into a target position among the above. Further, when manufacturing a cylindrical or spherical fuel or the like F, a small piece of fuel or the like may be formed.

  FIG.1 (d) shows an example of the apparatus for implementing 4th Embodiment of the lead removal method from the cement baking furnace concerning this invention, L / D of this kiln 10 is 0 in this apparatus. The charging port 4 provided in the region of 12 or less and a supply device (not shown) for supplying fuel or the like F to the charging port 4 are provided. The inlet 4 is configured to be opened only when it is positioned above the cement kiln 10 and performs material sealing or the like in order to minimize the amount of cold air taken into the cement kiln 10.

  Using such an inlet 4, fuel or the like F is directly supplied to a region where L / D is 0 or more and 12 or less, and the raw material temperature in the cement kiln 10 is 800 to 1100 ° C. as in the above embodiment. Lead in cement produced in cement kiln 10 can be reduced to a reduced atmosphere, lead volatility can be significantly increased, and lead can be recovered from chlorine bypass dust where lead is more concentrated than before. The content can be reduced.

In the above-described embodiment, when a fuel or the like is injected into a region where the L / D of the cement kiln 10 is 0 or more and 12 or less, the region where the raw material temperature in the cement kiln 10 is 800 to 1100 ° C. is set as a reducing atmosphere. However, the lead volatilization rate can be significantly increased by putting the above-described region into a reducing atmosphere without supplying fuel or the like. In actual operation of the cement kiln 10, the reduction of the region is performed. In order to maintain the atmosphere reliably, the O ₂ concentration of the combustion gas in the kiln bottom 10a of the cement kiln 10 is controlled to 5% or less and / or the CO concentration to 1000 ppm or more, and the L / D of the cement kiln 10 is 0 to 12 It is preferable to put fuel or the like in the following areas.

It is the schematic which shows the example of an apparatus for enforcing the lead removal method from the cement baking furnace concerning this invention. It is a flowchart which shows the whole structure of the chlorine bypass equipment attached to a cement baking furnace. It is the graph which computed the relationship between the gas temperature and the volatilization rate of lead by chemical equilibrium simulation. It is a graph which shows the relationship between the kiln bottom CO density | concentration and lead volatilization rate of a cement kiln. It is a graph showing the relationship between the kiln O ₂ concentration and lead volatilization rate of the cement kiln.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle 2 Long throwing device 3 Inclined surface 4 Slot 10 Cement kiln 10a Kiln bottom 11 Calciner 12 Lowermost cyclone 21 Probe 22 Cooling fan 23 Classifier 24 Dust collector 25 Exhaust fan

Claims (7)

Controlling the O ₂ concentration of the combustion gas in the kiln bottom of the cement kiln to 5% or less and / or the CO concentration to 1000 ppm or more,
In the vicinity of the kiln bottom of the cement kiln, an area where the raw material temperature in the cement kiln is 800 to 1100 ° C. is set as a reducing atmosphere,
A part of the combustion gas of the cement kiln is extracted to collect dust contained in the combustion gas;
A method for removing lead from a cement firing furnace, characterized in that lead is collected from the collected dust. While controlling the O ₂ concentration of the combustion gas in the kiln bottom of the cement kiln to 5% or less and / or the CO concentration to 1000 ppm or more,
When the inner diameter of the cement kiln is D, and the distance from the bottom end of the cement kiln to the kiln inside in the longitudinal direction is L,
2. The method for removing lead from a cement firing furnace according to claim 1, wherein a raw material containing fuel and / or combustible material is introduced into a region where the L / D of the cement kiln is 0 or more and 12 or less.   The raw material containing a powdery and / or slurry-like fuel and / or a combustible material is injected into a region where L / D of the cement kiln is 0 or more and 12 or less using a nozzle. To remove lead from cement firing furnaces.   The cement firing furnace according to claim 2, wherein a raw material containing a bulk fuel and / or a combustible material is thrown into a region where the L / D of the cement kiln is 0 or more and 12 or less using a long throw device. To remove lead from the surface.   A material containing a cylindrical or spherical fuel and / or a combustible material is introduced into an area where L / D of the cement kiln is 0 or more and 12 or less using an inclined surface of the kiln bottom of the cement kiln. The method for removing lead from a cement firing furnace according to claim 2.   6. The raw material containing a cylindrical or spherical fuel and / or combustible material is obtained by molding a raw material containing a small piece of fuel and / or combustible material. Lead removal method.   The cement kiln according to claim 2, wherein a raw material containing the fuel and / or combustible material is introduced from an inlet provided in a region where L / D of the cement kiln is 0 or more and 12 or less. Lead removal method.

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